Outline

Background: Previous observations revealed that gender and age corrected contributions of the singular components of repolarization may be associated to the risk of ventricular tachycardia.

Purpose: To further explore the possible physiological substrate of the singular components of repolarization.

Methods: We used 236 single beat surface map recordings in healthy subjects contributed by dr. F. Kornreich to the NEMY database. In each recording we performed a singular value decomposition of the matrix (leads vs time) of repolarization potentials. We then assigned to 0 all elements of the resulting matrices not belonging to the largest component and rebuilt the signal, obtaining a leads vs time potential matrix which we call 'the first orthogonal component', T1. T2 was computed in a similar way, from the second largest component.

Results: Figure 1 [Fig.Â 1] shows for each recording, the correlation between QRSi and T1i vs the correlation between QRSi and T2i. Ranges are .95 confidence intervals for the number of healthy recordings in which QRSi si better correlated to T2i (group A), to T1i (B) and not well correlated with either (C). The high correlation between QRSi and T2i in the A subgroup suggests that in these cases T2 might be generated by gradients of transmembrane potential secondary to ventricular activation. However, the same does not hold for groups B and C.

Conclusion: The physiologic substrate of the first two orthogonal components is variable in a subset of healthy individuals. This variability may be taken into account in order to further refine indices of repolarization heterogeneity based on singular value descomposition.